Honestly, in my opinion, babies are so wrapped up in
this new world, all the new things going in for
them, that a little cold (virus) hardly slows them down. it could be your baby is behind because she doesn't feel well all the time, and THAT is holding her back. Maybe not, but in either case I would push for them to figure it out. Chalking it all down to a virus is a lazy, sorry excuse.
My point is, YOU DO know your child more than anyone.